Reaction product of dithiophosphoric acid and dibasic acid anhydride



United States Patent 3,324,032 REACTION PRODUCT 0F DITHIOPHOSPHORIC ACID AND DIBASIC ACID ANHYDRIDE Rosemary OHalloran, Union, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Dec. 22, 1964, Ser. No. 420,445

8 Claims. (Cl. 252-46.6)

This invention relates to the reaction product'of dihydrocarbon dithiophosphoric acid and dibasic acid anhyof these additive derivatives are the metal salts, particularly zinc dialkyl dithiophosphate which is in wide spread use in lubricating oils because of its excellentantiwear, load-carrying and antioxidant properties. Recently the trend is to eliminate ash-forming additives in crankcase lubricating oils to thereby produce ashless lubricants which form less deposits in the engine than the corresponding metal containi qg, ash-forming lubricant. In view of this trend, a number of attempts have been made to make nonmetallic derivatives of dialkyl dithiophosphoric acids While retaining the sulfur and phosphorus content since these two elements appear to contribute substantially to the antiwear, load-carrying and antioxidant functions of the additive. Unfortunately, a number of these nonmetallic ashless dithiophosphoric acid derivatives have various disadvantages. For example, various dialkyl dithiophosphoric acids, which are too corrosive to be used in lubricants per se, have been neutralized with: alkylene oxides, e.g. propylene oxide; alkylene amines, e.g. ethylene diamine; ammonium salts, etc. However, these neutralized derivatives are corrosive to the copper-lead bearings that are frequently used in engines. The present invention is based upon the discovery that dihydrocarbon dithiophosphoric acid can be reacted with dicarboxylic acid anhydride to give an ashless product having good antioxidant, antiwear, and load-carrying properties, while at the same time having a low corrosivity to steel and copper-lead bearings.

The dihydrocarbon dithiophosphoric acids used in the invention include those of the formula:

Ros

wherein R represents the same or different hydrocarbon radicals of l to 30, preferably 2 to 12, carbon atoms each, including radicals such as aryl, alkyl, aralkyl and cycloalkyl radicals. Preferably, R represents alkyl groups, particularly those of 3 to 8 carbon atoms each. Usually, the total number of carbon atoms in both Rs will be sufficient so that the dihydrocarbon dithiophosphoric acid is soluble in mineral lubricating oil. Examples of such dihydrocarbon dithiophosphoric acids include diamyl dithiophos phoric acid; lauryl phenyl dithiophosphoric acid; diphenyl dithiophosphoric acid; dicapryl dithiophosphoric acid; dilauryl dithiophosphoric acid; amyl-butyl dithiophosphoric acid; di-C Oxo dithiophosphoric acid; etc.

The dibasic acid anhydride used in the invention can be aliphatic, aromatic, saturated or unsaturated, substituted 'or unsubstituted, containing 3 to 6 carbon atoms in the ring portion of the anhydride, which ring can be unsubstituted, or substituted. Examples of common anhydrldes which can be used include maleic anhydride, phthalic anhydride, succinic anhydride and alkenylsuccinic anhydride wherein the alkenyl groups can contain 1 to 250 carbon atoms.

The alkenylsuccinic anhydride, which is a preferred anhydride for the purpose of this invention, is readily prepared by reacting maleic anhydride with an organic compound having a double bond at one end, e.g. a polymer of a monoolefin, to thereby produce alkenylsuccinic anhydride having the formula:

wherein R is the alkenyl radical containing 1 to 250, preferably 50 to 250, carbon atoms. Because of its ready availability and low cost, R is preferably an alkenyl radical of a polymer of a C to C monoolefin. Examples of such' monoolefins are ethylene, propylene, l-butene, etc. i A particularly preferred alkenylsuccinic anhydride is polyisobutenyl succinic anhydride, the preparation of which is described in U.S. Patent No. 3,018,250, column 3, lines 57-71.

FIRST REACTION Additives of the invention can be made in a first reaction by reacting equi-molar amounts of the dihydrocarbon dithiophosphoric acid and the anhydride by simply mixing these two reactants, and heating for about 1 to 10 hours, usually 2 to 5 hours, at temperatures of to 400 F., preferably 200 to 300 F.

The above reaction is believed to proceed as follows, using succinic anhydride to typify the reaction:

ll C-CH;

ROS

The product produced by the first reaction of the in vention may or may not be mineral-oil-soluble, depending primarily upon its molecular weight and the size of the R groups of the dithiophosphoric acid and the type and size of the anhydride. If the product is oil-insoluble, it has been found that it can be adequately dispersed in oil by using it together with a lubricating oil ashless detergent additive.

SECOND REACTION where R" is selected from the group consisting of hydrogen,CH CI-I NH and The second reaction mentioned above, can be carried out by simply heating the first reaction product of the anhydride and dihydrocarbon dithiophosphoric acid, with the ammonia or amine, while removing water of condensation.

Lubricating oil compositions for crankcase use will comprise a major proportion of lubricating oil, and 0.01 to 20 wt. percent preferably 0.1 to wt. percent, of the additive of the invention. Oil concentrates may contain 20 to 80 wt. percent of the additive. For use in fields, such as gasoline and fuel oil, amounts of about .011 to 1.0 wt. percent of the additive will generally be used.

The oil component of the lubricating oil com-positions can be a mineral lubricating oil or a synthetic lubricating oil including diesters such as di-Z-ethylhexyl sebacate, complex esters, carbonate esters, polysilicones, and other synthetic oils.

The lubricating compositions of the invention can also include conventional lubricating oil additives in amounts of 0.05 to 10.0 wt. percent, usually 0.5 to 4.0 wt. percent each, based on the weight of the total composition. For example, oxidation inhibitors such as phenyl-alpha-naphthylamine; rust inhibitors such as sodium nitrite and lanolin; detergent additives such as basic calcium petroleum sulfonate, phosphosulfurized polyisobutylene, and barium phenate sulfide; visocity index improvers and pour depressants such as polymethacrylates; dyes; ashless sludge dispersants, etc. can be used.

The lubricating oil ashless sludge dispersants are particularly useful in practicing the present invention to solubilize or disperse normally oil-insoluble products of the aforesaid first reaction or the aforesaid second reaction. The more common ashless sludge dispersants are derivatives of polyamines such as high molecular weight amide and imide derivatives. Two types of these ashless sludge dispersant materials can be represented by the following word formulas:

Type I.Alkenylsuccinic anhydride-Polyalkylenamine- Acid or Aldehyde or Ketone and Type II.Alkenylsuccinic anhydride-Polyalkyleneamine.

In the Types I and II sludge dispersants represented above, the Alkenylsuccinic anhydride will usually contain 50 to 250 carbon atoms in the alkenyl group, while the polyalkyleneamine which is used is usually the same type as previously described for use in the aforesaid second reaction. The Acid component of Type I material can be either additional Alkenylsuccinic anhydride or a C to C preferably C to C mono or dicarboylic acid which can be branched or straight chain, saturated or unsaturated. Examples of such carboxylic acids include acetic acid, fumaric acid, caprie acid, adipic acid, lauric acid, oleic acid, linoleic acid, etc. The aldehydes or ketones which can be used as Type I components will usually have within the range of 1 to 10 carbon atoms and consist only of H. C and 0, such as formaldehyde and benzaldehyde.

Specific descriptions follow of Dispersant A (Type I) and Dispersant B (Type II) which were used in the working examples of the invention.

Dispersant A.This was a Type I dispersant prepared by condensing two molar proportions of polyisobutenyl succinic anhydride of about 1,300 molecular weight with one molar proportion of tetraethylene pentamine. The resulting ashless dispersant is represented by the word formula:

Polyisobutenyl succinic anhydride-tetraethylene pentamine-Polyisobutenyl succine anhydride.

Dispersant B.This was a dispersant of Type II prepared by condensing one mole of polyisobutenyl succinic anhydride with one mole of tetraethylene pentamine. This dispersant has the structure:

Where R is the alkenyl group of polyisobutylene of about 800 molecular weight.

Dispersants A and B were used in the following examples which include a preferred embodiment of the invention, and wherein all percents are by weight.

Example I Part A.Equal molar amounts of succinic anhydride and dialkyl dithiophosphoric acid were reacted together as follows: 273 grams of succinic anhydride, 682 grams of C /C dialkyldithiophosphoric acid, and 409 grams of a mineral lubricating oil having a viscosity of 100 SUS. at 210 F. as a diluent, were added to a 4-neck flask equipped with a condenser, thermometer and stirrer which was heated by a surrounding electrical mantle. Heating was initiated. After one hour, the temperature had risen to 290 F. and the reaction mixture had turned orange from its initial brown color. A small sample was withdrawn from the flask and cooled to room temperature. No crystals of succinic anhydride appeared thereby indicating that the reaction was complete. Otherwise, if there was unreacted succinic anhydride present, it would have crystallized out of solution on cooling due to its oil-insolubility at room temperature (77 F.). The heat was turned off, but the temperature of the reaction mass continued rising to 310 F. and then the reaction mass began to cool.

The 0. /C (amyl/isobutyl) dithiophosphoric acid consisted of about 65% primary amyl groups and about 35 wt. percent primary isobutyl groups and was formed by reacting P S with a mixture of 65 wt. percent amyl alcohol and 35 wt. percent isobutyl alcohol.

Part B.-When the temperature of the reaction mass of Part A had cooled from 310 F. to 230 F., the reaction mass was poured into 1364 grams of an oil concentrate consisting of about 70 wt. percent of the aforesaid Ashless Dispersant A dissolved in 30 Wt. percent of a mineral lubricating oil, said oil concentrate being at room temperature, i.e. 77 F. The resulting mixture was then stirred for 30 minutes and resulted in a product consisting of additive in oil, said product having a sulfur content of 5.62 wt. percent, a phosphorus content of 2.94 wt. percent; a pH of 3.6, and an ASTM-D-964 neutralization number of mg. KOH/ gm.

Part C.The aforementioned product of Part B in amounts sufficient to impart phosphorus concentrations of 0.03 and 0.06 wt. percent, based on the total composition, was then added to a base oil composition, hereinafter identified as Base Oil 1, and tested for antiwear characteristics in a Falex machine.

Base Oil 1.This base oil composition used was a fully formulated ashless automobile motor oil base except that it did not contain the usual antiwear additive. This motor oil base consisted of a major amount of mineral lubricating oil, an ashless sludge dispersant similar to Dispersant A, phosphosulfurized alpha-pinene as antioxidant, polyisobutylene as a V.I. improver, and a mixture of an alkyl fumarate-vinyl acetate copolymer and an acylated waxnaphthalene as pour point depressants.

Comparison samples were made up using Base Oil 1 and the zinc salt of the aforesaid C /C dialkyl dithiophosphoric acid, in phosphorus concentrations of 0.03 and 0.06 Wt. percent. The zinc C /C dialkyl dithiophosphate used in all the following examples was in the form of an oil concentrate consisting of about 75 wt, percent. of said dithiophosphate dissolved in about 25 wt. percent of mineral lubricating oil.

The Falex Wear test was carried out by running the test compositions in a Falex Wear test machine for 30 minutes under 500 lbs. direct guage reading. The wear test results obtained are summarized in the following Table I:

Base Oil'l per se gave a weight loss of 9.5 mg. of the steel test pin in the Falex machine, which pin also had deep scratches. The product of Example IB gave a weight loss of only 1.8 mg. at 0.03 wt. percent phosphorus concentration, and a loss of 2.4 mg. at 0.06 wt percent phosphorus concentration, while the test pins were still smooth and covered with a black protective coating. The zinc salt of the C /C dialkyl dithiophosphate also gave a good protective coating and good wear protection also, but not as good as the products of the invention.

Example I] Equi-molar amounts of di(isopropyl) dithiophosphoric acid and polyisobutenylsuccinic anhydride (said polyisobutenyl group having a molecular weight of 960) were re acted together for 4 hours at 200 F., and then cooled to room temperature. No oil diluent was used. The resulting product analyzed 3.05 wt. percent sulfur and 1.93 wt. percent phosphorus.

Example III Part A.-A series of valve train wear tests were carried out on Base Oil 1, i.e. the ashless motor oil base of Example I containing the product of Example II and for comparison 1.22 wt. percent of the zinc C /C dialkyl dithiophosphate concentrate (i.e. 75% dithiophosphate and 25% oil).

Part B.-A second series of valve train wear tests were carried out on a premium W-30 crankcase motor oil base hereinafter called Base Oil 2 containing the additives of Examples IB, II, and zinc C /C dialkyl dithiophosphate.

The aforesaid valve train wear tests were carried out as follows:

A 1960 Oldsmobile V-8 engine is operated for 10 minutes under'controlled conditions of speed, temperature, air-fuel ratio, etc., and is then shut off for 50 minutes. This cycle is carried out at a total of thirty times. Camshaft and lifters are then removed and examined for scuffing, while the lifters and lobes are measured for wear.

iii

The results of the preceding tests are summarized in the following Table H:

TABLE II Ave. Combined Cam and Lifter Wear Ave. Range Base Oil 1:

Plus 3.0 wt. percent Product Example II (0.057%

P 16 6-23 Plus 1.2 wt. percent Product Example II (0.023%

P 16 10-21 Plus 1.22 wt. percent zine 0 /0; dithiophosphate 5-483 Base Oil 2:

Plgs 2.0 wt. percent Product Example 113 (0.059% 2 0 P1:LP1)S 1.2 wt. percent Product Example II (0.023% 6 Pius'ifiiit'fbkleiif areogiegaiaiiasrasgrat (0.103% I) 2% As seen by the data of Table II, the products of the invention (Example IB and Example 11) were considerably more effective in phosphorus concentrations of 0.023 to 0.059% in reducing valve train wear than the conventionalzinc C /C dialkyl dithiophosphate in a phosphorus concentration of 0.103%.

Example IV Following the general procedure of Example I, Parts A and B, except that maleic anhydride was used in place of said succinic anhydride, equal molar amounts of maleic anhydride and the aforesaid C /C dialkyl dithiophosphoric acid were reacted.

Example V Following the general procedure of Example I, Part A, equal molar proportions of succinic anhydride and a di-Cg Oxo dithiophosphoric acid were reacted in the presence of an equal total weight of a mineral lubricating oil to give a product having 6.07 S and 3.31% P.

The di-C OX0 dithiophosphoric acid was made by treating C Oxo alcohol with P 8 C Oxo alcohol is an isomeric mixture of primary branched chain alcohols produced by the well-known Oxo alcohol process wherein polymers and copolymers of monoolefins such as propylene and butylene feed are reacted with CO and -H in the presence of a cobalt carbonyl catalyst to form a mixture of aldehydes which is then hydrogenated to Oxo alcohol.

The additive products of Examples IB, IV and V were tested in Base Oil 1 for their antioxidant properties. This test is carried out by air blowing for 5 days, a 40 cc. sample of the test oil containing a 19" strip of #14 gage copper wire and 2.2 gm. of iron powder as catalysts, in which test oil a small strip of aluminum is also immersed to detect varnish deposits. The results of this test are summarized in Table III which follows:

TABLE IIL-ANTIOXIDANT TEST 300 F., 5 DAYS Sludge I Varnish ]Neut.No.*

Base Oil 1, per se Base Oil+2.0% Product Ex. IB Base 0il+2.0% Product Ex. IV

Med. Hvy 1 8 .4

None 0 6 .3

None 0 5.1

Base 01l+1.8% Product Ex. V None 0 5 .8

*ASTM D-974.

Specifically, the height of each of the 16 lifters is measured and then averaged to determine the amount of lifter wear, Each of the 16 camshaft lobes is also measured and then averaged. These two averages are then added to give an average combined cam and lifter wear. An average combined cam and lifter wear below 40x10 inches is considered passing.

It is clear from Table III that the additives of the invention effectively act as oxidation inhibitors.

Example VI An additive was prepared by reacting equal molar proportions of didodecyl (C succinic anhydride and the C /C dialkyl dithiophosphoric acid following the general procedure of Example I-A. This additive, at 0.03% P in Base Oil 1 gave a Falex Wear weight loss of 5.0 mg. after 30 minutes at 500 pounds direct pressure, and at the 0.06% P concentration it gave a weight loss of 2.9 mg;

Example VI] A series of CLRL-38 tests were carried out in a one cylinder 'Labeco engine operating for 40 hours per test. This engine had conventional copper-lead bearings. The tests were carried out using Base Oil 1 containing the listed additives. The results of this test is summarized in the following Table IV.

TABLE IV Composition: Bearing Wt. loss, mg. Base Oil 1 94.3 +1.0% Product Ex. IB (029% P) 64.0 +1.22% zinc C /C dialkyl dithiophosphate (.103% P) 30.0

Table IV shows that the additives of the invention inhibit corrosion of copper and lead bearings of the type commonly used in internal combustion gasoline engines. Thus, Base Oil I per se showed a bearing weight loss of 94.3 mg. after 40 hours, while the product of Example I at a phosphorus level of only 0.029% P reduced the weight loss to 64 mg. While the zinc dithiophosphate reduced the loss to about 30 mg., this was at the much higher phosphorus level of .103% P.

In addition, the additives of the invention are non-corrosive to steel. Thus, a copped-lead bearing with a steel backing was suspended in Base Oil 1 containing 1.8 wt. percent of the additive product for Example V, and 0.625 gm. of lead oxide as catalyst, for 5 days at 300 F. Upon removal of the hearing, it was washed in solvent and exposed to a water saturated atmosphere for 7 days at room temperature. There was no rust on the steel backing after the test.

While the preceding shows the low corrosivity of the additives of the invention to copper-lead bearings, many prior dithiophosphoric acids derivatives are extremely corrosive. Thus, a C dialkyl dithiophosphoric acid neutralized with propylene oxide gave a bearing weight loss of over 3,000 mg. in the same Labeco engine L-38, while C Oxo dithiophosphoric acid neutralized with ethylene diamine gave a weight loss of 3226 mg.

Example VIII Part A.Equal molar proportions of di-C Oxo dithiophosphoric acid and polyisobutenyl succinic anhydride were reacted together in a manner similar to that described in Example II.

The dithiophosphoric acid was prepared from C Oxo alcohol which is an isomeric mixture of C branched chain primary alcohols produced by the 0x0 process (previously described) using a tetrapropylene feed.

The polyisobutenyl group of the succinic anhydride had a molecular weight of about 950.

Part B.Varying amounts of ethylene diamine and tetraethylene pentamine were reacted with the product of Part A by simple mixing and heating of 220 F. for about two hours while stirring. This amine treatment reduces the pH of the additive by converting the carbonyl group to an amine salt. This is illustrated by Table V which summarizes the result of this experiment.

TABLE V 98% product +2% tetraethylene pentamine 5.0

The above technique of reacting an amine with the acid reaction product is particularly useful where more neutral additives are required such as in turbine oils.

Example IX Pour gram moles of the aforesaid C /C dialkyl dithiophosphoric acid and four gram moles of polyisobutylene succinic anhydride (from polyisobutylene of about 960 mol. wt.) were heated together for three hours at 200 F., followed by one hour of additional heating at 250 F. The resulting product was cooled to room temperature and analyzed 3.92 wt. percent sulfur and 1.88 Wt. percent phosphorus.

Example X Maleic anhydride was reacted with dialkyl dithiophosphoric acid, wherein said alkyl groups were alkyl groups of C Oxo alcohol which is an isomeric mixture of primary, aliphatic, branched chain alcohols produced by the aforesaid Oxo process.

Specifically, 65 lbs. of the C Oxo alcohol was charged to the reactor and heated to F. Then 35 lbs. of P 8 was added over a 2 hour period while holding the reactor contents at a temperature between 150 and F. After all the P 8 was added, the temperature of the reactor contents was then raised to F., which temperature was then held for 2 hours. After this, the reactor contents, i.e. the resulting di-C Oxo dithiophosphoric acid was cooled to 140 F., and then removed from the reactor and filtered through filter paper mounted on a 1 sq. ft. laboratory filter press. The reactor was then rinsed with heptane and was recharged with 80 lbs. of the di-C Oxo dithiophosphoric acid prepared as above, and 26.7 lbs. of maleic anhydride. The reactor was then heated and the contents raised to a temperature of 150 F. at which point stirring was begun. The temperature of the reaction mixture was further raised to 200 R, which temperature was held for 7 hours, the last three hours of which a moderate vacuum was applied to the reactor. One percent, based on the reactor contents, of a commercial odorant was added, and the material was then cooled down without filtering, since filtering was not necessary. 105.5 lbs. of product was obtained, representing a 99% yield. This product was soluble in mineral lubricating oil in an amount of 3 wt. percent on the weight of oil. The product analyzed 8.05% phosphorus; 15.88 wt. percent sulfur; and had a pH of 2.9 and a neutralization number of 215 mg./KOH/gm., according to the method of ASTM D979.

Example XI The product of Example X in an amount of 1% in 99% of Base Oil 1, was tested for effectiveness as a crankcase lubricating oil in two new Dodge 6-cylinder taxicabs operating in New York city. Before testing, the valve lifters from the taxis were removed, measured and then replaced in the engine. After the test period, the valve lifters were again measured and the average lifter Wear was determined. For comparison, Base Oil 1 per se was run in two other similar taxicabs.

The result of the above taxicab test are summarized in As seen by the results of Table VI, the product of Example X was a very effective antiwear agent in actual use.

9 Example XII Following the general procedure of Example I, Part A, a series of additive products were made up by reacting equal molar amounts of the anhydride and dihydrocarbon dithiophosphoric acid. Some of these materials, together With the phosphorous and sulfur contents of the resulting product, are listed in the following Table VII.

TABLE VII Alkyl radical of the Ditiophos- Anhydride Percent P Percent S phoric Acid CisOxo Polyisobutenyl-suceinic 1. 2.0 CaOxo .do 2.0 3. 6 C13 OX0 1. 2.0

1. 42 1. 89 1. 93 3. 05 d0 2.03 3. 56 C7C n olefin substituted 2. 35 3.97

sucemlc. C Ox0 PolyisobutenyI-succinic.. 1. 89 2.08 C1 Oxo do 1.38 1.64 C1 Oxo do 1.38 1. 74 04 5- Succinic anhydride 3. 57 8. 34 C4 5. Iolyisobutenyl succi1 l. 89 3.88 C4 5 Succinic anydrida. 8. 57 14. 52 04 5 Dijdogecyl succinic anhy- 5. 98 10.18

The di-C 0x0, the di-C Oxo, and the C.,,/C dialkyl dithiophosphoric acids of Table VII, have all been previously described. The polyisobutenyl group of the succinic anhydrides of Table VII had a molecular weight of about 950.

Example XIII More additives were prepared by reaction of equal molar amounts of the aforesaid C /C dialkyl dithiophosphoric acid and anhydride, and then dispersing the reaction product in Dispersant A in a manner similar to that described in Example 1, Parts A and B. The additive products so prepared and their phosphorus and sulfur contents are listed in Table VIII which follows:

additive concentrates, said wt. percent being based on the total weight of the composition.

What is claimed is:

1. A composition selected from the group consisting of lubricating oils and normally liquid hydrocarbon fuels containing from about 0.001 to about 80 wt. percent of a reaction product prepared from reactants consisting only of a dihydrocarbon dithiophosphoric acid containmg a total of 2 to 31 carbon atoms and a dibasic acid anhydride having 3 to 6 carbon atoms in the ring portion of the anhydride and selected from the group consisting of unsubstituted anhydrides and anhydrides substituted with one to two hydrocarbon groups having a total of 1 to 250 carbon atoms, said reaction product being useful as an ashless additive and being prepared 'by heating together substantially equal molar amounts of said acid and said anhydride at a temperature in the range of about 150 to 400 F.

2. A composition according to claim 1, wherein said dihydrocarbon dithiophosphoric acid is dialkyl dithiophosphoric acid having 2 to 12 carbon atoms in each of said alkyl groups, and wherein said hydrocarbon groups of said anhydride are selected from the groups consisting of alkly and alkenyl radicals.

3. A composition according to claim 2, wherein each of said dialkyl groups of said dialkyl dithiophosphoric acid contain 3 to 8 carbon atoms, wherein said anhydride is alkenylsuccinic anhydride and said reaction product is formed by the reaction of substantially equal molar amounts of said dithiophosphoric acid and said anhydride.

4. A composition according to claim 3, wherein said alkenyl group is a polyisobutenyl group of to 250 carbon atoms.

5. A composition according to claim 1, wherein said composition is mineral oil and about 20 to 80 wt. percent of said reaction product is present to thereby form an additive concentrate.

TABLE VIII Percent Active Dithiophos- Anhydride Dispersant Percent P Percent S Ingredient phoric Acis Succinic A 3. 04 5. ----do A 2.94 5.62 A 2.90 5. 92

Example XIV 6. A composition according to claim 1, wherein said As a further illustration of the invention, 0.01 wt. percent of the product of Example 11 is added to 99.99 wt. percent of gasoline.

In summary, the present invention provides new types of additives by reacting a dihydrocarbon dithiophosphoric acid, preferably having a total of 2 to 31 carbon atoms in the molecule, with a substantially equal molar proportion of a dibasic acid anhydride having 3 to 6 carbon atoms in the anhydride ring portion of the molecule, which ring portion may be substituted with 1 to 2 hydrocarbon groups, preferably alkyl or alkenyl groups, which substituents contain a total of 1 to 250 carbon atoms. To illustrate, in the aforesaid polyisobutenyl succinic anhydride used in a number of the previous examples, the polyisobutenyl group is the substituent on the 4 carbon atom ring portion, i.e. the succinic anhydride portion. The resulting product can be used per se, or it can be mixed or dispersed in any proportion with a sludge dispersant to increase its oil or hydrocarbon solubility, or it can 'be further reacted with a small amount of amine, e.g. 0.1 to 5 wt. percent, to form an amine salt and make a more neutral product. In any case, the resulting final product can be used in hydrocarbon compositions such as lubricating oils, fuel oils, gasolines, etc.; in amounts ranging from 0.001 wt. percent in the case of gasoline up to as much as 80 wt. percent in the case of 2( 2)n[ 2)n]m 2 wherein n is 1 to 5 and m is 0 to 10, and wherein said alkenyl group contains about 50 to 200 carbon atoms.

References Cited UNITED STATES PATENTS 3,184,412 5/1965 Lowe et al. 25232.7 3,185,643 5/1965 Lowe et al. 252-32] X 3,185,645 5/1965 Clayton 252-32] X 3,219,666 11/1965 Norman et al. 252-515 X DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

1. A COMPOSITION SELECTED FROM THE GROUP CONSISTING OF LUBRICATING OILS AND NORMALLY LIQUID HYDROCARBON FUELS CONTAINING FROM ABOUT 0.001 TO ABOUT 80 WT. PERCENT OF A REACTION PRODUCT PREPARED FROM REACTANTS CONSISTING ONLY OF A DIHYDROCARBON DITHIOPHOSPHORIC ACID CONTAINING A TOTAL OF 2 TO 31 CARBON ATOMS AND A DIBASIC ACID ANHYDRIDE HAVING 3 TO 6 CARBON ATOMS IN THE RING PORTION OF THE ANHYDRIDE AND SELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED ANHYDRIDES AND ANHYDRIDES SUBSTITUTED WITH ONE TO TWO HYDROCARBON GROUPS HAVING A TOTAL OF 1 TO 250 CARBON ATOMS, SAID REACTION PRODUCT BEING USEFUL AS AN ASHLESS ADDITIVE AND BEING PREPARED BY HEATING TOGETHER SUBSTNATIALLY EQUAL MOLAR AMOUNTS OF SAID ACID AND SAID ANHYDRIDE AT A TEMPERATURE IN THE RANGE OF ABOUT 150* TO 400*F. 